Lewis John Stadler (July 6, 1896 – May 12, 1954) was an American geneticist. His research focused on the mutagenic effects of different forms of radiation on economically important plants like maize and barley.

While Stadler spent almost his entire academic life at the University of Missouri he was also involved in external activities. During the 1930s Stadler participated in efforts to bring European scientists to the U.S. to escape Nazism. In 1948 Stadler was appointed a delegate to the Eighth International Congress of Genetics, which met in Stockholm. However, the U.S. Department of Agriculture rejected his passport application and conducted a loyalty investigation; Stadler initially thought it was a State Department action.

Stadler married Cornelia Field Tuckerman in 1919. They had six children: Maury, Henry, David, John, Eliot, and Joan.

Although Stadler's initial research was on field plot technique and agronomy,[1] his main research interest became genetics, concentrated upon the study of mutation in corn. In 1925, he won a National Research Council Fellowship in Biology for a study in variation in linkage values in maize.[1] He did much work on the effects of X-ray treatments, and did comparative studies of mutation caused by X-rays and by ultraviolet rays.[3] His work earned him an international reputation.